Physiology · Reproduction, pregnancy and the fetus
Menopause !
- Regulation
- Exam priority: medium
Menopause is the end of periods when the ovaries run out of follicles; estrogen falls and the brain's signals to the ovary rise.
Updated 2026-11-01
Also called: Climacteric, Perimenopause
See it in 3D: Ovaries · Endometrium · Vagina · Hypothalamus
What it is
Menopause is the final menstrual period, confirmed after 12 months without menstruation, caused by depletion of ovarian follicles. As follicles run out, inhibin B and then estradiol fall, so FSH rises (first and most) and LH rises. The perimenopausal years before it bring irregular cycles; the years after, the effects of low estrogen on vessels, bone, the genitourinary tract and temperature control.
How it works, step by step
- The follicle pool falls with age through atresia; fewer growing follicles make less inhibin B.
- Less inhibin removes the brake on FSH: FSH rises and cycles shorten (faster follicle recruitment).
- Cycles become irregular and often anovulatory: unopposed estrogen phases alternate with low estrogen.
- When follicles are exhausted, estradiol and progesterone fall permanently and menses stop.
- Without estrogen feedback, LH and FSH stay high; estrone from fat becomes the main estrogen.
Hormone axes and feedback
Lesion Ovarian failure (menopause, Turner syndrome)Pattern GnRH ↑ · LH ↑ · FSH ↑ · E₂ ↓ · Progest. ↓ · Inhibin ↓
Primary hypofunction: Ovarian failure (menopause, Turner syndrome)
Pattern: GnRH ↑ · LH ↑ · FSH ↑ · E₂ ↓ · Progest. ↓ · Inhibin ↓
The target gland fails: its hormone falls and, without negative feedback, the pituitary and hypothalamic hormones rise. Estradiol ↓ with FSH ↑ (it rises more than LH, because inhibin is also lost) and LH ↑. Turner (45,X): streak ovaries, primary amenorrhea.
Exam rule: if the pituitary hormone moves opposite to the gland hormone, the problem is in the gland (primary); if they move together, it is central (pituitary or hypothalamus).
- Stimulates (+)
- Inhibits / negative feedback (−)
- Positive feedback (high E₂ at mid-cycle)
- Level ↑
- Level ↓
Typical values
| Parameter | Value | Note |
|---|---|---|
| Age at menopause | ≈48–52 years | median ≈51 years worldwide |
| Definition | 12 months without menses | retrospective |
| Premature ovarian insufficiency | <40 years | |
| FSH after menopause | >25–40 IU/L | laboratory cut-offs vary |
Approximate values for a healthy adult at rest; each laboratory sets its own ranges.
Regulation
- −Loss of inhibin B (fewer follicles): FSH rises early, before estradiol falls.
- −Loss of estradiol and progesterone: No negative feedback: LH and FSH remain high.
- +Aromatase in fat tissue: Estrone from adrenal androgens; more fat means more estrone.
Effects of low estrogen
| Target | Change | Consequence |
|---|---|---|
| Hypothalamus | Narrow thermoneutral zone | Hot flashes, night sweats, poor sleep |
| Bone | More resorption | Osteoporosis, fractures |
| Vagina and urethra | Thin epithelium, less glycogen, higher pH | Dryness, dyspareunia, urinary infections |
| Lipids and vessels | Higher LDL, less vasodilation | Rise in cardiovascular risk |
| Endometrium | Atrophy | Any bleeding after menopause needs study |
Clinical notes
- Turner syndrome (45,X) causes ovarian failure from childhood: primary amenorrhea with high FSH.
- Bleeding after menopause can come from atrophy, polyps, hyperplasia or endometrial cancer and is always investigated.
- Estrogen therapy in women with a uterus is combined with a progestogen, because unopposed estrogen causes endometrial hyperplasia.
Test yourself
Think of the answer, then tap the question to see it.
Why does FSH rise before LH in the menopausal transition?
The first change is loss of inhibin B from the shrinking follicle pool; inhibin selectively restrains FSH, so FSH rises while estradiol is still present.
Where does a postmenopausal woman's estrogen come from?
Mainly estrone, made by aromatase in fat tissue from adrenal androstenedione; obesity therefore raises postmenopausal estrogen and endometrial cancer risk.
Why does bone density fall quickly after menopause?
Estrogen restrains osteoclast formation and activity (via RANKL/OPG); its loss increases resorption more than formation.
See it in 3D
The structures of Durgical's 3D anatomy where it happens.
Related topics
- Actions of estrogen and progesterone
- The menstrual cycle: ovary and endometrium
- Bone remodeling
- Oogenesis, follicles and ovulation
- Body temperature regulation
Related conditions
In Biochemistry
Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.
Sources: 27.2 Anatomy and Physiology of the Ovarian Reproductive System (OpenStax (Rice University), 2022); Osteoporosis in Females (StatPearls (NCBI Bookshelf), 2025); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 82). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).
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Representative model, for educational purposes only.